fix: make E2E tests more stable

[martakam]

Many E2E tests failed because of timeouts, likely caused by running 8 workers running browsers at the same time.
This has now been decreased to 4.

Some tests also failed because we have a different menu in the header on mobiles now. This has been fixed by opening the menu and checking its content if we're testing on mobile screen sizes.

Furthermore, some smaller fixes highlighted by the accessibility checks from Axe have been implemented, and a slight refactoring of the E2E tests has been done.
All of these pass for me locally now, even though one must wait a little longer for the results. Please let me know if everything looks good for you guys as well.

Closes #120

[johahor]

I'm testing these right now, but some are failing for me. Currently working on a fix.

[hestro]

One test failed for me: “a user can log out and log in again” on Mobile Chrome. The failing step is logOut at fixtures.ts:86.

I ran the same test 10 times and got 6 passes and 4 fails. AI suggested the flaky test is a timing issue, which fits the failure snapshot, where the menu has already closed when the test looks for “Log out”.

[johahor]

Try now @hestro

[hestro]

@johahor
The test that failed earlier doesn't seem to fail anymore - good!

However, when I ran all the e2e tests three times, I got three different results:

Run 1:

3 failed
[firefox] › e2e/accessibility.spec.ts:46:5 › light mode › home page
[firefox] › e2e/accessibility.spec.ts:89:5 › light mode › profile page
[webkit] › e2e/home.spec.ts:7:1 › searching from the hero shows matching books

2 skipped
195 passed (1.8m)

Run 2:

2 skipped
198 passed (1.6m)

Run 3:

1 failed
[firefox] › e2e/accessibility.spec.ts:89:5 › light mode › profile page

2 skipped
197 passed (1.6m)

There still seem to be some flaky tests...

[martakam]

We can reduce the amount of workers even more, because the timeouts/failures are usually caused by that.

@hestro could you try decrasing the number 4 to 1 and see if that fixes it?

T37-Project-2/frontend/playwright.config.ts

Line 23 in f8c01fd

workers: process.env.CI ? 1 : 4,